(1) Field of the Invention
The present invention pertains to a head suspension for supporting a read/write head adjacent a rotating data storage device, and in particular to a head suspension design that decreases the pitch and roll stiffness of the read/write head support while maintaining a desirable lateral and vertical stiffness of the head suspension.
(2) Description of the Related Art
Most personal computer systems today employ direct access storage devices (DASD) or rigid disk drives for data storage. A conventional disk drive contains a spindle that is rotated by an electric motor at several thousand revolutions of the spindle per minute. One or more magnetically coated recording disks are mounted on the spindle for rotation therewith at axially spaced positions along the spindle.
Positioned adjacent the rotating disks is a head actuator column. The head actuator column typically has a plurality of actuator arms thereon, and each actuator arm supports one or more head suspensions that extend in cantilever fashion from the actuator arm to distal ends of the head suspension. The head suspensions are very precise metal springs that hold read/write heads, such as magnetic or optical heads, adjacent the rotating disks in the disk drive. The head suspensions are typically comprised of a proximal support region that attaches the head suspension to an actuator arm, a distal load region that supports that read/write head, and an intermediate spring region that biases the load region and the read/write head toward the rotating disk. The read/write heads are attached to sliders at the distal ends of each of the head suspensions. The read/write heads of this type usually do not contact the surface of the rotating disk (although contact heads and/or sliders are also used), but instead "fly" on the slider at a precisely maintained microscopic distance above the rotating disk surface. The head suspension maintains the read/write head at a correct flying distance from the surface of the rotating disk because of an equilibrium created between the upward force of an air bearing created by air driven under the slider by the rotation of the disk, and a downward spring bias force applied by the head suspension that is dependent on the head suspension's vertical stiffness.
The surface of a data storage disk is not perfectly flat. The principal function of a head suspension flexure or load beam gimbal is to be compliant in the pitch and roll directions to maintain the slider at its proper attitude and to follow disk surface fluctuations as well as to reduce the effect of load beam motion on the slider. Typically, the pitch motion is permitted by rotation of the slider about a transverse axis to the head suspension and the roll motion is permitted by rotation of the slider about a longitudinal axis to the head suspension.
As slider sizes decrease in size, the supporting air bearing created beneath these sliders also decreases in size, resulting in a decrease in the lift force exerted on the slider. With the lift force of the air bearing decreasing, head suspensions must be designed to be more sensitive to the external torques applied to the slider. In prior art head suspensions, this has been accomplished by reducing the stiffness of the head suspension flexure or load beam gimbal.
The head suspension flexure or gimbal must also have a high lateral (transverse) stiffness to prevent unintended motion of its attached read/write head due to acceleration and deceleration forces exerted on the slider when the head suspension is rapidly moved to position the read/write head at different radial locations on the disk. Even though sliders are becoming increasingly smaller and their mass is becoming smaller, the increased acceleration and deceleration forces cannot be ignored. Also, a high lateral stiffness is required to prevent motion of the slider due to the air flow created by the rotating disk. As disks in disk drives are positioned closer together and their revolution speeds are increased, the air flow created by their rotation is increased. Even though the side surface area of the slider is decreasing, it is not enough to counter the increase in air flow.
It is also necessary that a head suspension have a high vertical stiffness or handling stiffness. This stiffness is required to minimize vertical movement of the head suspension and possible damage to the head suspension from routine handling and from ultrasonic cleaning processes.
Therefore, as head suspension flexures or gimbals are developed having a low pitch and roll stiffnesses for smaller sliders, steps must be taken to avoid reducing the lateral stiffness of the flexure or gimbal without also negatively affecting vertical stiffness thereof. Unfortunately, in the present design of head suspension flexures and load beam gimbals, the lateral and vertical stiffness characteristics are coupled to their pitch and roll stiffness characteristics. If there is a need to change one stiffness component, then another one is also changed. For this reason, the present design of head suspension flexures and load beam gimbals results in a compromise in stiffness due to the difficulty of obtaining the optimum stiffness combinations.
It would therefore be desirable to design a head suspension flexure or load beam gimbal in which the pitch and roll stiffness of the read/write head support is decreased while the lateral stiffness and the vertical stiffness of the flexure or gimbal are maintained at desirable values.